1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to the structure and use of bipolar forceps and other instruments for coagulating, cutting, and necrosing tissue.
Electrosurgery refers broadly to a class of medical procedures which rely on the application of high frequency electrical energy, usually radiofrequency energy, to patient tissue to achieve a number of possible effects, such as cutting, coagulation, hyperthermia, necrosis, and the like. Of particular interest to the present invention, bipolar electrosurgical devices rely on contacting electrodes of different polarity in close proximity to each other against or into tissue. For example, bipolar forceps 100 (FIGS. 1 and 2) have been used for cutting and coagulating tissue, where the opposed jaws 102 and 104 of the forceps are connected to different poles of an electrosurgical power supply. The high frequency electrical current thus flows from one jaw to the other through the tissue present therebetween. Use of such bipolar forceps is effective for a number of purposes and advantageous in that its effect is generally limited to the tissue held between the jaws. Heating, however, is not totally limited to such intermediate tissue, and in some instances heating of adjacent tissues can be problematic. Such heating occurs because the current flows not only between the jaws but also laterally outward, as shown by flux lines F in FIG. 1B.
Various improvements to bipolar forceps have been proposed. For example, the placement of pins or other tissue-penetrating elements onto the tissue-engaging surface(s) of either or both jaws has been suggested for a variety of purposes. Regardless of the intended purpose, the placement of tissue-penetrating elements on the jaw(s) can marginally focus the current density and somewhat lessen heating of adjacent tissues. Such prior designs employing tissue-penetrating elements, however, still cause unwanted heating of adjacent tissues in at least certain circumstances.
A second problem with conventional bipolar forceps is limited power delivery. With conventional forceps, jaws having a length of about 20 mm and a width of about 5 mm can usually deliver only 25 W of power without causing charring of the tissue. Charring greatly increases electrical resistance through the tissue and can result in premature termination of the treatment. With such a low power level, the time to fully coagulate the tissue can be excessive.
It would therefore be desirable to provide still further improved bipolar forceps and other electrosurgical device designs. In particular, it would be desirable to provide bipolar forceps which provide a very high degree of focused heating, i.e., provide heating of tissue between the jaws with minimized heating of tissue adjacent to the jaws. It would be further desirable to provide bipolar forceps which can deliver higher current flows and densities to the tissue being treated without charring the tissue and terminating the current flow. Such device designs should be relatively simple and easy to fabricate. The devices and methods should be compatible with conventional electrosurgical power supplies and usable in a wide variety of procedures, including cutting, coagulation, and necrosis, where the localized and specific heating of patient tissues is desired. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
Bipolar forceps having penetrating elements on opposed jaws thereof are described in U.S. Pat. Nos. 5,527,313 and 5,217,460; Soviet Union Patent Publication SU 197711; and French Patent No. 598,149. Bipolar electrosurgical instruments having laterally spaced-apart electrodes on opposed jaws are described in U.S. Pat. Nos. 5,833,690; 5,702,390; 5,688,270; and 5,403,312. A blood vessel coagulation device having electrode arrays on opposed jaws of forceps is described in U.S. Pat. No. 5,151,102. Other bipolar electrosurgical devices are described in U.S. Pat. Nos. 5,797,941; 5,665,085; 5,662,680; 5,582,611; 5,445,638; 5,441,499; 5,383,876; 5,403,312; 5,098,431; and 4,043,342. A radiofrequency tumor heating device comprising parallel electrode arrays of opposite polarity is described in U.S. Pat. No. 4,016,886.